1 //===-- SystemZShortenInst.cpp - Instruction-shortening pass --------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This pass tries to replace instructions with shorter forms. For example,
10 // IILF can be replaced with LLILL or LLILH if the constant fits and if the
11 // other 32 bits of the GR64 destination are not live.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "SystemZTargetMachine.h"
16 #include "llvm/CodeGen/LiveRegUnits.h"
17 #include "llvm/CodeGen/MachineFunctionPass.h"
18 #include "llvm/CodeGen/MachineInstrBuilder.h"
19 #include "llvm/CodeGen/TargetRegisterInfo.h"
20
21 using namespace llvm;
22
23 #define DEBUG_TYPE "systemz-shorten-inst"
24
25 namespace {
26 class SystemZShortenInst : public MachineFunctionPass {
27 public:
28 static char ID;
29 SystemZShortenInst();
30
31 bool processBlock(MachineBasicBlock &MBB);
32 bool runOnMachineFunction(MachineFunction &F) override;
getRequiredProperties() const33 MachineFunctionProperties getRequiredProperties() const override {
34 return MachineFunctionProperties().set(
35 MachineFunctionProperties::Property::NoVRegs);
36 }
37
38 private:
39 bool shortenIIF(MachineInstr &MI, unsigned LLIxL, unsigned LLIxH);
40 bool shortenOn0(MachineInstr &MI, unsigned Opcode);
41 bool shortenOn01(MachineInstr &MI, unsigned Opcode);
42 bool shortenOn001(MachineInstr &MI, unsigned Opcode);
43 bool shortenOn001AddCC(MachineInstr &MI, unsigned Opcode);
44 bool shortenFPConv(MachineInstr &MI, unsigned Opcode);
45 bool shortenFusedFPOp(MachineInstr &MI, unsigned Opcode);
46
47 const SystemZInstrInfo *TII;
48 const TargetRegisterInfo *TRI;
49 LiveRegUnits LiveRegs;
50 };
51
52 char SystemZShortenInst::ID = 0;
53 } // end anonymous namespace
54
55 INITIALIZE_PASS(SystemZShortenInst, DEBUG_TYPE,
56 "SystemZ Instruction Shortening", false, false)
57
createSystemZShortenInstPass(SystemZTargetMachine & TM)58 FunctionPass *llvm::createSystemZShortenInstPass(SystemZTargetMachine &TM) {
59 return new SystemZShortenInst();
60 }
61
SystemZShortenInst()62 SystemZShortenInst::SystemZShortenInst()
63 : MachineFunctionPass(ID), TII(nullptr) {
64 initializeSystemZShortenInstPass(*PassRegistry::getPassRegistry());
65 }
66
67 // Tie operands if MI has become a two-address instruction.
tieOpsIfNeeded(MachineInstr & MI)68 static void tieOpsIfNeeded(MachineInstr &MI) {
69 if (MI.getDesc().getOperandConstraint(1, MCOI::TIED_TO) == 0 &&
70 !MI.getOperand(0).isTied())
71 MI.tieOperands(0, 1);
72 }
73
74 // MI loads one word of a GPR using an IIxF instruction and LLIxL and LLIxH
75 // are the halfword immediate loads for the same word. Try to use one of them
76 // instead of IIxF.
shortenIIF(MachineInstr & MI,unsigned LLIxL,unsigned LLIxH)77 bool SystemZShortenInst::shortenIIF(MachineInstr &MI, unsigned LLIxL,
78 unsigned LLIxH) {
79 Register Reg = MI.getOperand(0).getReg();
80 // The new opcode will clear the other half of the GR64 reg, so
81 // cancel if that is live.
82 unsigned thisSubRegIdx =
83 (SystemZ::GRH32BitRegClass.contains(Reg) ? SystemZ::subreg_h32
84 : SystemZ::subreg_l32);
85 unsigned otherSubRegIdx =
86 (thisSubRegIdx == SystemZ::subreg_l32 ? SystemZ::subreg_h32
87 : SystemZ::subreg_l32);
88 unsigned GR64BitReg =
89 TRI->getMatchingSuperReg(Reg, thisSubRegIdx, &SystemZ::GR64BitRegClass);
90 Register OtherReg = TRI->getSubReg(GR64BitReg, otherSubRegIdx);
91 if (!LiveRegs.available(OtherReg))
92 return false;
93
94 uint64_t Imm = MI.getOperand(1).getImm();
95 if (SystemZ::isImmLL(Imm)) {
96 MI.setDesc(TII->get(LLIxL));
97 MI.getOperand(0).setReg(SystemZMC::getRegAsGR64(Reg));
98 return true;
99 }
100 if (SystemZ::isImmLH(Imm)) {
101 MI.setDesc(TII->get(LLIxH));
102 MI.getOperand(0).setReg(SystemZMC::getRegAsGR64(Reg));
103 MI.getOperand(1).setImm(Imm >> 16);
104 return true;
105 }
106 return false;
107 }
108
109 // Change MI's opcode to Opcode if register operand 0 has a 4-bit encoding.
shortenOn0(MachineInstr & MI,unsigned Opcode)110 bool SystemZShortenInst::shortenOn0(MachineInstr &MI, unsigned Opcode) {
111 if (SystemZMC::getFirstReg(MI.getOperand(0).getReg()) < 16) {
112 MI.setDesc(TII->get(Opcode));
113 return true;
114 }
115 return false;
116 }
117
118 // Change MI's opcode to Opcode if register operands 0 and 1 have a
119 // 4-bit encoding.
shortenOn01(MachineInstr & MI,unsigned Opcode)120 bool SystemZShortenInst::shortenOn01(MachineInstr &MI, unsigned Opcode) {
121 if (SystemZMC::getFirstReg(MI.getOperand(0).getReg()) < 16 &&
122 SystemZMC::getFirstReg(MI.getOperand(1).getReg()) < 16) {
123 MI.setDesc(TII->get(Opcode));
124 return true;
125 }
126 return false;
127 }
128
129 // Change MI's opcode to Opcode if register operands 0, 1 and 2 have a
130 // 4-bit encoding and if operands 0 and 1 are tied. Also ties op 0
131 // with op 1, if MI becomes 2-address.
shortenOn001(MachineInstr & MI,unsigned Opcode)132 bool SystemZShortenInst::shortenOn001(MachineInstr &MI, unsigned Opcode) {
133 if (SystemZMC::getFirstReg(MI.getOperand(0).getReg()) < 16 &&
134 MI.getOperand(1).getReg() == MI.getOperand(0).getReg() &&
135 SystemZMC::getFirstReg(MI.getOperand(2).getReg()) < 16) {
136 MI.setDesc(TII->get(Opcode));
137 tieOpsIfNeeded(MI);
138 return true;
139 }
140 return false;
141 }
142
143 // Calls shortenOn001 if CCLive is false. CC def operand is added in
144 // case of success.
shortenOn001AddCC(MachineInstr & MI,unsigned Opcode)145 bool SystemZShortenInst::shortenOn001AddCC(MachineInstr &MI, unsigned Opcode) {
146 if (LiveRegs.available(SystemZ::CC) && shortenOn001(MI, Opcode)) {
147 MachineInstrBuilder(*MI.getParent()->getParent(), &MI)
148 .addReg(SystemZ::CC, RegState::ImplicitDefine | RegState::Dead);
149 return true;
150 }
151 return false;
152 }
153
154 // MI is a vector-style conversion instruction with the operand order:
155 // destination, source, exact-suppress, rounding-mode. If both registers
156 // have a 4-bit encoding then change it to Opcode, which has operand order:
157 // destination, rouding-mode, source, exact-suppress.
shortenFPConv(MachineInstr & MI,unsigned Opcode)158 bool SystemZShortenInst::shortenFPConv(MachineInstr &MI, unsigned Opcode) {
159 if (SystemZMC::getFirstReg(MI.getOperand(0).getReg()) < 16 &&
160 SystemZMC::getFirstReg(MI.getOperand(1).getReg()) < 16) {
161 MachineOperand Dest(MI.getOperand(0));
162 MachineOperand Src(MI.getOperand(1));
163 MachineOperand Suppress(MI.getOperand(2));
164 MachineOperand Mode(MI.getOperand(3));
165 MI.removeOperand(3);
166 MI.removeOperand(2);
167 MI.removeOperand(1);
168 MI.removeOperand(0);
169 MI.setDesc(TII->get(Opcode));
170 MachineInstrBuilder(*MI.getParent()->getParent(), &MI)
171 .add(Dest)
172 .add(Mode)
173 .add(Src)
174 .add(Suppress);
175 return true;
176 }
177 return false;
178 }
179
shortenFusedFPOp(MachineInstr & MI,unsigned Opcode)180 bool SystemZShortenInst::shortenFusedFPOp(MachineInstr &MI, unsigned Opcode) {
181 MachineOperand &DstMO = MI.getOperand(0);
182 MachineOperand &LHSMO = MI.getOperand(1);
183 MachineOperand &RHSMO = MI.getOperand(2);
184 MachineOperand &AccMO = MI.getOperand(3);
185 if (SystemZMC::getFirstReg(DstMO.getReg()) < 16 &&
186 SystemZMC::getFirstReg(LHSMO.getReg()) < 16 &&
187 SystemZMC::getFirstReg(RHSMO.getReg()) < 16 &&
188 SystemZMC::getFirstReg(AccMO.getReg()) < 16 &&
189 DstMO.getReg() == AccMO.getReg()) {
190 MachineOperand Lhs(LHSMO);
191 MachineOperand Rhs(RHSMO);
192 MachineOperand Src(AccMO);
193 MI.removeOperand(3);
194 MI.removeOperand(2);
195 MI.removeOperand(1);
196 MI.setDesc(TII->get(Opcode));
197 MachineInstrBuilder(*MI.getParent()->getParent(), &MI)
198 .add(Src)
199 .add(Lhs)
200 .add(Rhs);
201 return true;
202 }
203 return false;
204 }
205
206 // Process all instructions in MBB. Return true if something changed.
processBlock(MachineBasicBlock & MBB)207 bool SystemZShortenInst::processBlock(MachineBasicBlock &MBB) {
208 bool Changed = false;
209
210 // Set up the set of live registers at the end of MBB (live out)
211 LiveRegs.clear();
212 LiveRegs.addLiveOuts(MBB);
213
214 // Iterate backwards through the block looking for instructions to change.
215 for (MachineInstr &MI : llvm::reverse(MBB)) {
216 switch (MI.getOpcode()) {
217 case SystemZ::IILF:
218 Changed |= shortenIIF(MI, SystemZ::LLILL, SystemZ::LLILH);
219 break;
220
221 case SystemZ::IIHF:
222 Changed |= shortenIIF(MI, SystemZ::LLIHL, SystemZ::LLIHH);
223 break;
224
225 case SystemZ::WFADB:
226 Changed |= shortenOn001AddCC(MI, SystemZ::ADBR);
227 break;
228
229 case SystemZ::WFASB:
230 Changed |= shortenOn001AddCC(MI, SystemZ::AEBR);
231 break;
232
233 case SystemZ::WFDDB:
234 Changed |= shortenOn001(MI, SystemZ::DDBR);
235 break;
236
237 case SystemZ::WFDSB:
238 Changed |= shortenOn001(MI, SystemZ::DEBR);
239 break;
240
241 case SystemZ::WFIDB:
242 Changed |= shortenFPConv(MI, SystemZ::FIDBRA);
243 break;
244
245 case SystemZ::WFISB:
246 Changed |= shortenFPConv(MI, SystemZ::FIEBRA);
247 break;
248
249 case SystemZ::WLDEB:
250 Changed |= shortenOn01(MI, SystemZ::LDEBR);
251 break;
252
253 case SystemZ::WLEDB:
254 Changed |= shortenFPConv(MI, SystemZ::LEDBRA);
255 break;
256
257 case SystemZ::WFMDB:
258 Changed |= shortenOn001(MI, SystemZ::MDBR);
259 break;
260
261 case SystemZ::WFMSB:
262 Changed |= shortenOn001(MI, SystemZ::MEEBR);
263 break;
264
265 case SystemZ::WFMADB:
266 Changed |= shortenFusedFPOp(MI, SystemZ::MADBR);
267 break;
268
269 case SystemZ::WFMASB:
270 Changed |= shortenFusedFPOp(MI, SystemZ::MAEBR);
271 break;
272
273 case SystemZ::WFMSDB:
274 Changed |= shortenFusedFPOp(MI, SystemZ::MSDBR);
275 break;
276
277 case SystemZ::WFMSSB:
278 Changed |= shortenFusedFPOp(MI, SystemZ::MSEBR);
279 break;
280
281 case SystemZ::WFLCDB:
282 Changed |= shortenOn01(MI, SystemZ::LCDFR);
283 break;
284
285 case SystemZ::WFLCSB:
286 Changed |= shortenOn01(MI, SystemZ::LCDFR_32);
287 break;
288
289 case SystemZ::WFLNDB:
290 Changed |= shortenOn01(MI, SystemZ::LNDFR);
291 break;
292
293 case SystemZ::WFLNSB:
294 Changed |= shortenOn01(MI, SystemZ::LNDFR_32);
295 break;
296
297 case SystemZ::WFLPDB:
298 Changed |= shortenOn01(MI, SystemZ::LPDFR);
299 break;
300
301 case SystemZ::WFLPSB:
302 Changed |= shortenOn01(MI, SystemZ::LPDFR_32);
303 break;
304
305 case SystemZ::WFSQDB:
306 Changed |= shortenOn01(MI, SystemZ::SQDBR);
307 break;
308
309 case SystemZ::WFSQSB:
310 Changed |= shortenOn01(MI, SystemZ::SQEBR);
311 break;
312
313 case SystemZ::WFSDB:
314 Changed |= shortenOn001AddCC(MI, SystemZ::SDBR);
315 break;
316
317 case SystemZ::WFSSB:
318 Changed |= shortenOn001AddCC(MI, SystemZ::SEBR);
319 break;
320
321 case SystemZ::WFCDB:
322 Changed |= shortenOn01(MI, SystemZ::CDBR);
323 break;
324
325 case SystemZ::WFCSB:
326 Changed |= shortenOn01(MI, SystemZ::CEBR);
327 break;
328
329 case SystemZ::WFKDB:
330 Changed |= shortenOn01(MI, SystemZ::KDBR);
331 break;
332
333 case SystemZ::WFKSB:
334 Changed |= shortenOn01(MI, SystemZ::KEBR);
335 break;
336
337 case SystemZ::VL32:
338 // For z13 we prefer LDE over LE to avoid partial register dependencies.
339 Changed |= shortenOn0(MI, SystemZ::LDE32);
340 break;
341
342 case SystemZ::VST32:
343 Changed |= shortenOn0(MI, SystemZ::STE);
344 break;
345
346 case SystemZ::VL64:
347 Changed |= shortenOn0(MI, SystemZ::LD);
348 break;
349
350 case SystemZ::VST64:
351 Changed |= shortenOn0(MI, SystemZ::STD);
352 break;
353
354 default: {
355 int TwoOperandOpcode = SystemZ::getTwoOperandOpcode(MI.getOpcode());
356 if (TwoOperandOpcode == -1)
357 break;
358
359 if ((MI.getOperand(0).getReg() != MI.getOperand(1).getReg()) &&
360 (!MI.isCommutable() ||
361 MI.getOperand(0).getReg() != MI.getOperand(2).getReg() ||
362 !TII->commuteInstruction(MI, false, 1, 2)))
363 break;
364
365 MI.setDesc(TII->get(TwoOperandOpcode));
366 MI.tieOperands(0, 1);
367 if (TwoOperandOpcode == SystemZ::SLL ||
368 TwoOperandOpcode == SystemZ::SLA ||
369 TwoOperandOpcode == SystemZ::SRL ||
370 TwoOperandOpcode == SystemZ::SRA) {
371 // These shifts only use the low 6 bits of the shift count.
372 MachineOperand &ImmMO = MI.getOperand(3);
373 ImmMO.setImm(ImmMO.getImm() & 0xfff);
374 }
375 Changed = true;
376 break;
377 }
378 }
379
380 LiveRegs.stepBackward(MI);
381 }
382
383 return Changed;
384 }
385
runOnMachineFunction(MachineFunction & F)386 bool SystemZShortenInst::runOnMachineFunction(MachineFunction &F) {
387 if (skipFunction(F.getFunction()))
388 return false;
389
390 const SystemZSubtarget &ST = F.getSubtarget<SystemZSubtarget>();
391 TII = ST.getInstrInfo();
392 TRI = ST.getRegisterInfo();
393 LiveRegs.init(*TRI);
394
395 bool Changed = false;
396 for (auto &MBB : F)
397 Changed |= processBlock(MBB);
398
399 return Changed;
400 }
401